German document DE 10 2009 026 973 A1 discusses a brake system for a motor vehicle and a method for controlling it. The brake system includes an hydraulic service brake system having a master brake cylinder and multiple wheel brakes connected to the master brake cylinder and an electromechanical service brake system having electromechanical brakes. In addition, the brake system also has a mechanical brake booster situated on the master brake cylinder. In the event of a failure of the hydraulic service brake system, braking a vehicle equipped with the brake system is still to be possible using the electromechanical service brake system. At the same time, it is to be possible, using the electromechanical brake booster, to generate a force acting against a brake pedal actuation in such a way that a driver of the vehicle still senses a resistance when depressing the brake pedal. In this manner, in particular a leakage in the hydraulic system is to be imperceptible to the driver of the vehicle.